I decided to gather together this data in response to the recent discussion on the use of alternate fuels to run a glass studio.

My occassional sarcastic comments on that issue were based on the fact that I have yet to see a technology that I could readily put to use, and on my belief that good design using conventional fuels and known technology can gain as much if not more than 'cheaper' fuels using technology that has unknown variables and problems.

I believe electric furnaces in particular, where all the energy can be contained in a small unit that is sealed when not in use, can yield results equal to if not better than 'alternative technologies'.

Heat loss is a combination of the insulation value of the material, the square footage of the outside walls, and the leakage around doors, etc.

In a well designed electric melter, with the interior space only slightly larger than the crucible, and using the best insulation materials, the actual energy use would be substantially lower than a furnace that used waste oil that fired into a large firebox (creating perhaps 3X the interior volume), and that was insulated with higher density castable to take the extra abuse.

Replacing Kastolite 30 with 2600°F IFB would cut the heat loss almost in half on its own. Replacing 6 lb fiber with Skamol board would gain another 30%. The Skamol is also very cheap. Cutting the interior volume in half or more would also drop the heat loss substantially.

I have edited this post to add the figures for one of the Microporuos Insulation products from Thermal Ceramics, BTU Block Board.

Here Are The Insulation Values Of Different Materials
(Btu·in/hr·ft2·°F)

David this was a valuable contribution. The information is out there but needs to complied and presented like this for comparison.
Not too many years ago electric melting was very experimental. Industry had used it for years but getting down to the studio level took time. The contollers had to be discovered and every way of using electricity required experimentation.
Right now in fuels, everything except natural gas and propane seem to have the "alternative" label. Once again though industry has worked all of this out on their scale just not on ours. The same is true for recuperation. Economics is driving us to be exploratory and experimental but we aren't really creating nuclear fusion. Fortunately, we can get most of the high tech materials and refractories if we can find out about them. It is putting all of these together that will give us the best results. Every time I rebuild, I do it differently. I am running a studio now for less than three times what it cost in 1972. With our recent cost increase, propane is over eight times as expensive as it was then. Materials, design and some innovation are all pieces in the puzzle.

One more to check out is Microporuos Insulation from Thermal Ceramics. Henry pointed this one out a while back. They claim it has the "lowest thermal conductivity of any known insulation". It comes in a variety of forms including a hand formable BTU-GUE. I didn't see any numbers on it though.

Microporuos is the heading of the line of insulating materials sold by Thermal Ceramics. It is an insulating material unlike any other type of material any of us are used to. The subheading that is applicable to us is the line called Flexible Min-K._Specifically you will look at the MIX F150 and MIX F182. You can find it at the following link. Oh yes Franklin, no don't rigidize it.

So I was wondering if Henry, or anybody else has any direct experience with it. The heat loss figures are about a third of the Skamol Board, which had been the best of the lot. The question is whether the incredible heat loss figures actually work in practise.

You can download a data sheet about it and other Thermal Ceramics products here:

Yes I believe the heat loss figures put out by TC are accurate. We use about 1/2 inch on the crown of the EZtherm furnace and considering it in other locations as well. You have to be careful though where you put it as it max's out at about 1800 deg. F. so you do not want to put it in any area that gets to that temperature, directly on furnace crowns, etc. We now use it as the last layer of our crown. It is my belief that in some situations the energy savings $$$$$ will more than pay for the upfront cost. It is fragile to the degree that one should handle it carefully. It is the type of material that does not bend easily although it will somewhat. It is best used in flat crown or wall situations. The space saving from standard fiber is terrific.

One issue in designing furnaces for minimum heat loss is the following issue:

If you replace 6" of Kastoloite 30 with 3" of IFB which has one half the heat loss, is this a break even situation?

Logic would say that since the Kastolite furnace is much larger on the outside, the larger radiating area would loose more heat. But how much more?

The issue becomes important when you look at using an expensive product like the microporous insulation in place of several inches of 6 lb fiber, which is very cheap.

Does anybody have either theoretical or practical knowledge on this issue? If you spend a lot of money on high tech materials, are you just saving space, or is there substantial real savings on energy consumption?

Please allow me to tell a story related to your post.
I just got a piece of grey boad and was told that it is silicaboard and the btu/ft hr deg F is .11 at 1832 F. That sounds too good to be true. Is that posible. Any guesses what it is?
They are building a new plant and I get to wallow in the garbage, found some scraps no specs and no one will say what it is.
Its a pig delight now to find some ears to show Pete.

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